CN112255778A - Superfine-diameter large-depth-of-field high-resolution endoscopic optical imaging system - Google Patents
Superfine-diameter large-depth-of-field high-resolution endoscopic optical imaging system Download PDFInfo
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- CN112255778A CN112255778A CN202011220855.7A CN202011220855A CN112255778A CN 112255778 A CN112255778 A CN 112255778A CN 202011220855 A CN202011220855 A CN 202011220855A CN 112255778 A CN112255778 A CN 112255778A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
- G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
- G02B23/2407—Optical details
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
- G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
- G02B23/2407—Optical details
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- G02B23/243—Objectives for endoscopes
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Abstract
The invention relates to an ultra-fine-diameter large-depth-of-field high-resolution endoscopic optical imaging system which comprises a first lens, a second lens, a diaphragm, a third lens, a fourth lens, an infrared filter and chip protective glass, wherein the first lens, the second lens, the third lens and the fourth lens are all spherical lenses which are arranged in sequence from an object side and are separated by taking air as an interval, the first lens has negative focal power, the object side surface of the first lens is a plane, and the image side surface of the first lens is a concave surface; the second lens has positive focal power, and the object side surface of the second lens is a convex surface; the third lens has negative focal power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface; the fourth lens has positive focal power, and the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the maximum effective radius of the object side surface of the first lens is less than or equal to 0.5; the number F of the lens of the endoscopic optical imaging system is 5-8. The invention has the advantages of super-fine diameter, large scene depth and high resolution, compact structure, convenient processing and installation and good imaging quality.
Description
Technical Field
The invention relates to the technical field of endoscopic optical imaging systems, in particular to an endoscopic optical imaging system with superfine diameter, large depth of field and high resolution.
Background
With the development of scientific technology, medical endoscopes undergo a transition from rigid medical endoscopes to fiber optic endoscopes to electronic endoscopes. The lens is an important component of the medical endoscope, and the quality of the imaging quality of the lens directly influences the using effect of the endoscope. And for the endoscope device, it will be developed toward miniaturization, wide observation range, high performance, and the like. The endoscope is a medical detection device which is commonly used at present, can enter a position to be detected with pathological changes through a natural pore canal of a human body, and can carry out real-time dynamic imaging on the pathological changes, but is limited by the structure of the human body, cannot be reached in the routine endoscopic detection of a narrow area, and causes discomfort to the human body, so that the smaller the volume of the endoscope is, the smaller the discomfort to the human body is, and the market has higher competitiveness.
Disclosure of Invention
The invention aims to provide an ultra-fine-diameter large-depth-of-field high-resolution endoscopic optical imaging system which is provided with a lens with ultra-fine diameter, large depth of field and high resolution, wherein an ultra-fine-diameter endoscope can reach a thinner cavity of a human body, and meanwhile, the large depth of field can realize high-resolution imaging in a larger working range, so that the diagnosis accuracy is improved.
The purpose of the invention is realized by the following technical scheme:
the endoscopic optical imaging system is characterized by comprising a first lens, a second lens, a diaphragm, a third lens, a fourth lens, an infrared filter and chip protective glass which are sequentially arranged from an object side, wherein the first lens, the second lens, the third lens and the fourth lens are all spherical lenses and are separated and arranged at intervals of air, the first lens has negative focal power, the object side surface of the first lens is a plane, and the image side surface of the first lens is a concave surface; the second lens has positive focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface; the third lens has negative focal power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface; the fourth lens has positive focal power, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the maximum effective radius of the object side surface of the first lens is less than or equal to 0.5; the number F of the lens of the endoscopic optical imaging system is 5-8.
Furthermore, the full field angle of the endoscopic optical imaging system is 75-105 degrees, the maximum aperture of the lens is 1.0mm, the working distance is 2-50 mm, and the total length of the lens is less than or equal to 3.0 mm.
Further, the endoscopic optical imaging system satisfies the following relationship:
ET12＞0.15mm；
ET34＞0.07mm；
0.45<R7≤0.95；
R2≥0.45；
R6>0.45；
ET2>0.37mm；
ET12 is an air gap between edges of the first lens element and the second lens element, ET34 an air gap between edges of the third lens element and the fourth lens element, R7 is a radius of curvature of an object-side surface of the fourth lens element, R2 is a radius of curvature of an image-side surface of the first lens element, R6 is a radius of curvature of an image-side surface of the third lens element, and ET2 is a thickness of a side of the second lens element.
Further, the endoscopic optical imaging system satisfies the following relationship:
2.5<f*TAN(HFOV)/T34<7.5；
where f is the effective focal length of the endoscopic optical imaging system, T34 is the air space between the third lens and the fourth lens on the optical axis, and HFOV is half of the maximum field angle of the endoscopic optical imaging system.
Further, the endoscopic optical imaging system satisfies the following relationship:
0.5mm<f*TAN(HFOV)<0.8mm；
wherein f is the effective focal length of the endoscopic optical imaging system, and the HFOV is half of the maximum field angle of the endoscopic optical imaging system.
Further, the endoscopic optical imaging system satisfies the following relationship:
-6.5≤f3/f<-1.5；
1.2<f4/f<1.5；
-5.0<(f3/f+f2/f)<-0.5；
wherein f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, and f is the effective focal length of the endoscopic optical imaging system.
Further, the endoscopic optical imaging system satisfies the following relationship:
-2.5<R4/R3<-0.5；
1.0<(R5+R6)/R7≤7.0；
-2.0<(R7-R8)/(R7+R8)<22.0；
wherein R3 is the radius of curvature of the object-side surface of the second lens element, R4 is the radius of curvature of the image-side surface of the second lens element, R5 is the radius of curvature of the object-side surface of the third lens element, R6 is the radius of curvature of the image-side surface of the third lens element, R7 is the radius of curvature of the object-side surface of the fourth lens element, and R8 is the radius of curvature of the image-side surface of the fourth lens element.
Further, the endoscopic optical imaging system satisfies the following relationship:
2.0<∑CT/CT2<3.5；
0.45<∑CT/TTL<0.6；
wherein Σ CT is the sum of the center thicknesses of the first lens element to the fourth lens element on the optical axis, CT2 is the center thickness of the second lens element on the optical axis, and TTL is the on-axis distance from the object-side surface of the first lens element to the image plane.
Further, the endoscopic optical imaging system satisfies the following relationship:
0.5<|f12/f34|<4.5；
where f12 is the combined focal length of the first lens and the second lens, and f34 is the combined focal length of the third lens and the fourth lens.
Further, the endoscopic optical imaging system satisfies the following relationship:
0.3<DT41/∑AT<1.0；
where DT41 is the maximum effective radius of the object-side surface of the fourth lens, and Σ AT is the sum of the air spaces on the optical axis between any adjacent two lenses of the first lens to the fourth lens.
The invention has the following beneficial effects:
(1) the invention can ensure that the endoscopic optical imaging system has good imaging quality by limiting the surface types and the focal powers of the first lens, the second lens, the third lens and the fourth lens; the endoscopic optical imaging system can have the characteristic of ultra-thin diameter by limiting the maximum effective radius of the object side surface of the first lens; the endoscopic optical imaging system has the characteristic of large depth of field by properly adjusting the effective focal length and the entrance pupil diameter of the endoscopic optical imaging system;
(2) the invention can make the endoscopic optical imaging system meet the processing requirements of optics and structure size by limiting the curvature radius of the first lens, the third lens and the fourth lens, the air gap from the edge of the image side surface of the first lens to the edge of the object side surface of the second lens and the air gap from the edge of the image side surface of the third lens to the edge of the object side surface of the fourth lens;
(3) the invention further optimizes the imaging quality of the endoscopic optical imaging system by optimizing the parameters of the effective focal length of the endoscopic optical imaging system, the combined focal length among the lenses, the curvature radius of the image side surface of the lens, the central thickness on the optical axis of the lens, the maximum effective radius of the object side surface of the lens and the like, so that the lens is miniaturized and meets the processing performance.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and embodiments.
Fig. 1 is a schematic structural diagram of embodiment 1 of the present invention.
Fig. 2 is a graph of axial chromatic aberration in example 1 of the present invention.
Fig. 3 is an astigmatism graph of embodiment 1 of the present invention.
Fig. 4 is a distortion graph of embodiment 1 of the present invention.
FIG. 5 is a MTF graph of example 1 of the present invention.
Fig. 6 is a schematic structural diagram of embodiment 2 of the present invention.
Fig. 7 is a graph of the on-axis color difference in embodiment 2 of the present invention.
Fig. 8 is an astigmatism graph of embodiment 2 of the present invention.
Fig. 9 is a distortion graph of embodiment 2 of the present invention.
FIG. 10 is a MTF graph of example 2 of the present invention.
Fig. 11 is a schematic structural diagram of embodiment 3 of the present invention.
Fig. 12 is a graph of the on-axis color difference in embodiment 3 of the present invention.
Fig. 13 is an astigmatism graph of embodiment 3 of the present invention.
Fig. 14 is a distortion graph of embodiment 3 of the present invention.
FIG. 15 is a MTF graph of example 3 of the present invention.
Fig. 16 is a schematic structural diagram of embodiment 4 of the present invention.
Fig. 17 is an on-axis color difference chart of embodiment 4 of the present invention.
Fig. 18 is an astigmatism graph of embodiment 4 of the present invention.
Fig. 19 is a distortion graph of embodiment 4 of the present invention.
FIG. 20 is a MTF graph of example 4 of the present invention.
Fig. 21 is a schematic structural diagram of embodiment 5 of the present invention.
Fig. 22 is an on-axis color difference chart of embodiment 5 of the present invention.
Fig. 23 is an astigmatism graph of embodiment 5 of the present invention.
Fig. 24 is a distortion graph of embodiment 5 of the present invention.
FIG. 25 is a MTF graph of example 5 of the present invention.
Detailed Description
As shown in fig. 1, 6, 11, 16 and 21, the superfine-diameter large-depth-of-field high-resolution endoscopic optical imaging system comprises a first lens E1, a second lens E2, a stop STO, a third lens E3, a fourth lens E4, an infrared filter E5 and a chip protection glass E6 which are sequentially arranged from an object side, wherein the first lens E1, the second lens E2, the third lens E3 and the fourth lens E4 are all spherical lenses and are respectively arranged at intervals of air, the first lens E1 has negative focal power, an object side surface S1 of the first lens is a plane, and an image side surface S2 of the first lens E2 is a concave surface; the second lens E2 has positive power, and has a convex object-side surface S3 and a convex image-side surface S4; the third lens E3 has negative power, and has a convex object-side surface S5 and a concave image-side surface S6; the fourth lens E4 has positive power, and has a convex object-side surface S7 and a convex image-side surface S8; filter E5 has object side S9 and image side S10; the chip protection glass E6 has an object side S11 and an image side S12. Light from the object plane OBJ of the object passes through the respective surfaces S1 to S12 in sequence and is finally imaged on the imaging plane S13. The maximum effective radius of the object side surface of the first lens E1 is less than or equal to 0.5; the number F of the lens of the endoscopic optical imaging system is 5-8. The full field angle of the endoscopic optical imaging system is 75-105 degrees, the maximum aperture of the lens is 1.0mm, the working distance is 2-50 mm, and the total length of the lens is less than or equal to 3.0 mm.
The endoscopic optical imaging system can have good imaging quality by limiting the surface types and the focal powers of the first lens E1, the second lens E2, the third lens E3 and the fourth lens E4; the endoscopic optical system can have the characteristic of ultra-thin diameter by limiting the maximum effective radius of the object side surface of the first lens E1; by appropriately adjusting the effective focal length and the entrance pupil diameter, i.e., the F number of the lens, of the endoscopic optical imaging system, the endoscopic optical imaging system can be made to have a large depth of field characteristic.
The endoscopic optical imaging system satisfies the following relationship:
(1)ET12＞0.15mm；
ET34＞0.07mm；
0.45<R7≤0.95；
R2≥0.45；
R6>0.45；
ET2>0.37mm。
ET12 is an air gap at the edge of the first lens E1 and the second lens E2, ET34 is an air gap at the edge of the third lens E3 and the fourth lens E4, and R7 is a radius of curvature of an object-side convex surface of the fourth lens E4; r2 is the first lens E1 concave image side radius of curvature, R6 is the third lens E3 concave image side radius of curvature, ET2 is the edge thickness of the second lens.
The invention can enable the endoscopic optical imaging system to meet the processing requirements of optics and structure size by limiting the curvature radius of the first lens E1, the third lens E3 and the fourth lens E4, and an air gap from the edge of the image side surface of the first lens E1 to the edge of the object side surface of the second lens E2 and an air gap from the edge of the image side surface of the third lens E3 to the edge of the object side surface of the fourth lens E4.
(2)2.5<f*TAN(HFOV)/T34<7.5；
Where f is an effective focal length of the endoscopic optical imaging system, T34 is an air space on an optical axis between the third lens E3 and the fourth lens E4, and HFOV is half of a maximum field angle of the endoscopic optical imaging system.
The invention optimizes the air space of the third lens E3 and the fourth lens E4 on the optical axis and limits the image height, so that the system has the characteristics of high resolution and easy processing.
(3)0.5mm<f*TAN(HFOV)<0.8mm；
Wherein f is the effective focal length of the endoscopic optical imaging system, and the HFOV is half of the maximum field angle of the endoscopic optical imaging system.
The invention can effectively compress the size of the system by reasonably distributing half of the effective focal length and the maximum field angle of the endoscopic optical imaging system, so that the light deflection angle is small.
(4)-6.5≤f3/f<-1.5；
1.2<f4/f<1.5；
-5.0<(f3/f+f2/f)<-0.5；
Wherein f2 is the effective focal length of the second lens E2, f3 is the effective focal length of the third lens E3, f4 is the effective focal length of the fourth lens E4, and f is the effective focal length of the endoscopic optical imaging system.
The invention can reasonably control the contribution range of the focal power of the third lens E3 and the effective focal length ratio range of the endoscopic optical imaging system, and simultaneously reasonably control the contribution rate of the positive spherical aberration of the third lens E3, so that the negative focal power generated by the positive lens can be reasonably balanced.
According to the invention, by restraining the ratio of the focal power of the fourth lens E4 to the effective focal length of the endoscopic optical imaging system within a reasonable range, the spherical aberration generated by the first three lenses can be balanced by the residual spherical aberration after balancing, the spherical aberration of the system can be finely adjusted and controlled, and the accurate control of the on-axis field aberration is enhanced.
According to the invention, by reasonably controlling the range of the sum of the focal length ratio of the third lens E3 and the effective focal length ratio of the endoscopic optical imaging system and the focal length of the second lens E2 and the effective focal length ratio of the endoscopic optical imaging system, reasonable positive third-order spherical aberration and negative fifth-order spherical aberration can be contributed, and the negative third-order spherical aberration and the positive fifth-order spherical aberration generated by the second lens E2 and the third lens E3 are balanced, so that the system has smaller spherical aberration, and good imaging quality of an on-axis view field is ensured.
(5)-2.5<R4/R3<-0.5；
1.0<(R5+R6)/R7≤7.0；
-2.0<(R7-R8)/(R7+R8)<22.0；
Wherein R3 is the radius of curvature of the object-side surface of the second lens element E2, R4 is the radius of curvature of the image-side surface of the second lens element E2, R5 is the radius of curvature of the object-side surface of the third lens element E3, R6 is the radius of curvature of the image-side surface of the third lens element E3, R7 is the radius of curvature of the object-side surface of the fourth lens element E4, and R8 is the radius of curvature of the image-side surface of the fourth lens element E4.
According to the invention, by limiting the ratio range of the curvature radii of the object side surface and the image side surface of the second lens E2, the shape of the second lens E2 can be effectively constrained, so that the aberration contribution rates of the object side surface and the image side surface of the second lens E2 are effectively controlled, the aberration related to the aperture zone of the system is effectively balanced, and the imaging quality of the system is effectively improved.
By controlling the curvature radius of the object side surface and the image side surface of the third lens E3 and the fourth lens E4, the invention can reasonably control the incident angle of the chief ray of each field of view of the endoscopic optical imaging system on the image surface, and meet the requirement of designing the chief ray incident angle of the endoscopic optical imaging system.
According to the invention, by controlling the curvature radius of the object side surface and the curvature radius of the image side surface of the fourth lens E4 within a reasonable range, the contribution of the astigmatism of the object side surface and the image side surface can be effectively controlled, and further, the image quality of the intermediate field and the image quality of the aperture zone can be effectively and reasonably controlled.
(6)2.0<∑CT/CT2<3.5；
0.45<∑CT/TTL<0.6；
Σ CT is the sum of the central thicknesses of the first lens E1 to the fourth lens E4 on the optical axis, CT2 is the central thickness of the second lens E2 on the optical axis, and TTL is the on-axis distance from the object side surface of the first lens E1 to the image plane.
The invention not only ensures the requirement of processing performance, but also meets the requirement of lens miniaturization by restricting the ratio of the sum of the central thicknesses of all the lenses on the optical axis to the central thickness of the second lens E2 on the optical axis within a reasonable range.
The invention can reasonably control the residual distortion range after balance by controlling the ratio range of the sum of the central thicknesses of all the lenses on the optical axis and the total length of the optical system, so that the system has good distortion performance.
(7)0.5<|f12/f34|<4.5；
Where f12 is a combined focal length of the first lens E1 and the second lens E2, and f34 is a combined focal length of the third lens E3 and the fourth lens E4.
The invention ensures the excellent image quality of the system and the good processability of the system by limiting the ratio range of the combined focal length of the first lens E1 and the second lens E2 and the combined focal length of the third lens E3 and the fourth lens E4.
(8)0.3<DT41/∑AT<1.0；
Where DT41 is the largest effective radius of the object side surface of the fourth lens E4, and Σ AT is the sum of the air intervals on the optical axis between any two adjacent lenses of the first lens E1 to the fourth lens E4.
According to the invention, the size of the lens can be reduced, the miniaturization of the lens is met, and the resolving power is improved by reasonably controlling the maximum effective radius of the object side surface of the fourth lens E4 and the sum of the air intervals on the optical axis between any two adjacent lenses from the first lens E1 to the fourth lens E4.
Example 1
The surface type, radius of curvature, thickness, half-diameter and material of each lens of this example are shown in table 1.
Table 1 example 1 endoscopic optical imaging system lens parameters
| Flour mark | Surface type | Radius of curvature (mm) | Thickness (mm) | Semi-aperture (mm) | Material |
| OBJ | Spherical surface | All-round | 2.0000 | 2.9220 | |
| S1 | Spherical surface | All-round | 0.3000 | 0.5000 | 1.74,52.6 |
| S2 | Spherical surface | 0.4500 | 0.3479 | 0.3101 | |
| S3 | Spherical surface | 0.8139 | 0.5715 | 0.2534 | 1.76,27.5 |
| S4 | Spherical surface | -1.1473 | 0.0536 | 0.1156 | |
| STO | Spherical surface | All-round | 0.0253 | 0.0785 | |
| S5 | Spherical surface | 0.9023 | 0.3000 | 0.0920 | 1.76,27.5 |
| S6 | Spherical surface | 0.5000 | 0.0733 | 0.1539 | |
| S7 | Spherical surface | 0.9383 | 0.4065 | 0.2396 | 1.62,56.7 |
| S8 | Spherical surface | -0.7935 | 0.0500 | 0.3377 | |
| S9 | Spherical surface | All-round | 0.3000 | 0.3667 | 1.52,64.1 |
| S10 | Spherical surface | All-round | 0.0300 | 0.4141 | |
| S11 | Spherical surface | All-round | 0.4000 | 0.4214 | 1.52,64.1 |
| S12 | Spherical surface | All-round | 0.0400 | 0.4873 | |
| S13 | Spherical surface | All-round | 0.4962 |
Example 2
The surface type, radius of curvature, thickness, half-diameter and material of each lens of this example are shown in table 2.
Table 2 example 2 endoscopic optical imaging system lens parameters
| Flour mark | Surface type | Radius of curvature (mm) | Thickness (mm) | Semi-aperture (mm) | Material |
| OBJ | Spherical surface | All-round | 2.0000 | 2.7290 | |
| S1 | Spherical surface | All-round | 0.3000 | 0.5000 | 1.74,49.2 |
| S2 | Spherical surface | 0.4500 | 0.2486 | 0.3163 | |
| S3 | Spherical surface | 1.0333 | 0.6847 | 0.2906 | 1.76,27.5 |
| S4 | Spherical surface | -0.9865 | 0.1262 | 0.1541 | |
| STO | Spherical surface | All-round | 0.0248 | 0.0795 | |
| S5 | Spherical surface | 0.7821 | 0.3000 | 0.0902 | 1.76,27.5 |
| S6 | Spherical surface | 0.5000 | 0.0756 | 0.1500 | |
| S7 | Spherical surface | 0.9500 | 0.3898 | 0.2276 | 1.64,55.5 |
| S8 | Spherical surface | -0.8606 | 0.0655 | 0.3215 | |
| S9 | Spherical surface | All-round | 0.3000 | 0.3548 | 1.52,64.1 |
| S10 | Spherical surface | All-round | 0.0365 | 0.4038 | |
| S11 | Spherical surface | All-round | 0.4000 | 0.4133 | 1.52,64.1 |
| S12 | Spherical surface | All-round | 0.0540 | 0.4831 | |
| S13 | Spherical surface | All-round | 0.4950 |
Example 3
The surface type, radius of curvature, thickness, half-diameter and material of each lens of this example are shown in table 3.
Table 3 example 3 endoscopic optical imaging system lens parameters
Example 4
The surface type, radius of curvature, thickness, half-diameter and material of each lens of this example are shown in table 4.
Table 4 example 4 endoscopic optical imaging system lens parameters
| Flour mark | Surface type | Radius of curvature (mm) | Thickness (mm) | Semi-aperture (mm) | Material |
| OBJ | Spherical surface | All-round | 2.0000 | 2.9220 | |
| S1 | Spherical surface | All-round | 0.3000 | 0.5000 | 1.74,52.6 |
| S2 | Spherical surface | 0.4500 | 0.3479 | 0.3101 | |
| S3 | Spherical surface | 0.8139 | 0.5715 | 0.2534 | 1.76,27.5 |
| S4 | Spherical surface | -1.1473 | 0.0536 | 0.1156 | |
| STO | Spherical surface | All-round | 0.0253 | 0.0785 | |
| S5 | Spherical surface | 0.9023 | 0.3000 | 0.0920 | 1.76,27.5 |
| S6 | Spherical surface | 0.5000 | 0.0733 | 0.1539 | |
| S7 | Spherical surface | 0.9383 | 0.4065 | 0.2396 | 1.62,56.7 |
| S8 | Spherical surface | -0.7935 | 0.0500 | 0.3377 | |
| S9 | Spherical surface | All-round | 0.3000 | 0.3667 | 1.52,64.1 |
| S10 | Spherical surface | All-round | 0.0300 | 0.4141 | |
| S11 | Spherical surface | All-round | 0.4000 | 0.4214 | 1.52,64.1 |
| S12 | Spherical surface | All-round | 0.0400 | 0.4873 | |
| S13 | Spherical surface | All-round | 0.4962 |
Example 5
The surface type, radius of curvature, thickness, half-diameter and material of each lens of this example are shown in table 5.
TABLE 5 EXAMPLE 5 endoscopic optical imaging System lens parameters
Table 6 shows basic data of the endoscopic optical imaging system according to examples 1 to 5.
TABLE 6 basic data of endoscopic optical imaging system of each embodiment
| Basic data/embodiment | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 |
| f1(mm) | -0.65 | -0.61 | -0.74 | -0.60 | -0.67 |
| f2(mm) | 0.81 | 0.78 | 0.70 | 0.72 | 0.78 |
| f3(mm) | -2.81 | -3.38 | -1.34 | -2.19 | -3.35 |
| f4(mm) | 0.78 | 0.77 | 1.05 | 0.76 | 0.94 |
| f(mm) | 0.63 | 0.56 | 0.74 | 0.54 | 0.74 |
| TTL(mm) | 2.91 | 3.00 | 2.99 | 2.90 | 2.95 |
| ImgH(mm) | 0.50 | 0.50 | 0.50 | 0.50 | 0.60 |
| HFOV(°) | 45.14 | 48.44 | 38.57 | 50.80 | 44.97 |
Wherein f is an effective focal length of the endoscopic optical imaging system, f1 is an effective focal length of the first lens E1, f2 is an effective focal length of the second lens E2, f3 is an effective focal length of the third lens E3, f4 is an effective focal length of the fourth lens E4, TTL is an on-axis distance from an object side surface of the first lens E1 to an imaging surface, ImgH is a half-image height of the endoscopic optical imaging system, and HFOV is half of a maximum field angle of the endoscopic optical imaging system.
In the above examples 1 to 5, the endoscopic optical imaging system satisfies the conditions of table 7.
TABLE 7 relation of conditions of endoscopic optical imaging system according to each example
For embodiment 1, fig. 2 is an axial chromatic aberration curve of an optical imaging lens, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 3 is an astigmatism curve of the optical imaging lens, which shows meridional field curvature and sagittal field curvature. Fig. 4 is a distortion curve of the optical imaging lens, which represents corresponding distortion magnitude values at different image heights. Fig. 5 is an MTF curve of the optical imaging lens, which shows MTF values in a central field of view, a meridian direction of 0.5 field of view, a sagittal direction of 0.5 field of view, a meridian direction of 1.0 field of view, and a sagittal direction of 1.0 field of view at different spatial frequencies, where a full field angle corresponding to 1.0 field of view is 90.3 °.
For embodiment 2, fig. 7 is an on-axis chromatic aberration curve of an optical imaging lens, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 8 is an astigmatism curve of the optical imaging lens, which shows meridional field curvature and sagittal field curvature. Fig. 9 is a distortion curve of the optical imaging lens, which represents the corresponding distortion magnitude values at different image heights. Fig. 10 is an MTF curve of the optical imaging lens, which shows MTF values in a central field of view, a meridian direction of 0.5 field of view, a sagittal direction of 0.5 field of view, a meridian direction of 1.0 field of view, and a sagittal direction of 1.0 field of view at different spatial frequencies, where a full field angle corresponding to 1.0 field of view is 96.9 °.
For embodiment 3, fig. 12 is an on-axis chromatic aberration curve of an optical imaging lens, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 13 is an astigmatism curve of the optical imaging lens, which shows meridional field curvature and sagittal field curvature. Fig. 14 is a distortion curve of the optical imaging lens, which represents corresponding distortion magnitude values at different image heights. Fig. 15 is an MTF curve of the optical imaging lens, which shows MTF values in a central field of view, a 0.5 field of view meridional direction, a 0.5 field of view sagittal direction, a 1.0 field of view meridional direction, and a 1.0 field of view sagittal direction at different spatial frequencies, where a full field angle corresponding to a 1.0 field of view is 77.1 °.
For embodiment 4, fig. 17 is an on-axis chromatic aberration curve of an optical imaging lens, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 18 is an astigmatism curve of the optical imaging lens, which shows meridional field curvature and sagittal field curvature. Fig. 19 is a distortion curve of the optical imaging lens, which shows the corresponding distortion magnitude values at different image heights. Fig. 20 is an MTF curve of the optical imaging lens, which shows MTF values in a central field of view, a meridian direction of 0.5 field of view, a sagittal direction of 0.5 field of view, a meridian direction of 1.0 field of view, and a sagittal direction of 1.0 field of view at different spatial frequencies, where a full field angle corresponding to 1.0 field of view is 102.6 °.
For example 5, fig. 22 is an on-axis chromatic aberration curve of an optical imaging lens, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 23 is an astigmatism curve of the optical imaging lens, which shows meridional field curvature and sagittal field curvature. Fig. 24 is a distortion curve of the optical imaging lens, which shows the corresponding distortion magnitude values at different image heights. Fig. 25 is an MTF curve of the optical imaging lens, which shows MTF values in a central field of view, a meridian direction of 0.5 field of view, a sagittal direction of 0.5 field of view, a meridian direction of 1.0 field of view, and a sagittal direction of 1.0 field of view at different spatial frequencies, where a full field angle corresponding to 1.0 field of view is 90.0 °.
In conclusion, the endoscopic optical imaging system has the lens with ultra-small diameter, large depth of field and high resolution, has compact structure, convenient processing and installation and good imaging quality, and meets the requirements of miniaturization, light weight and wide angle of a medical endoscope.
The above description is illustrative and not restrictive. Many modifications and variations of the present invention will be apparent to those skilled in the art in light of the above teachings, which will fall within the spirit and scope of the invention.
Claims (10)
1. The endoscopic optical imaging system is characterized by comprising a first lens, a second lens, a diaphragm, a third lens, a fourth lens, an infrared filter and chip protective glass which are sequentially arranged from an object side, wherein the first lens, the second lens, the third lens and the fourth lens are all spherical lenses and are separated and arranged at intervals of air, the first lens has negative focal power, the object side surface of the first lens is a plane, and the image side surface of the first lens is a concave surface; the second lens has positive focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface; the third lens has negative focal power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface; the fourth lens has positive focal power, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the maximum effective radius of the object side surface of the first lens is less than or equal to 0.5; the number F of the lens of the endoscopic optical imaging system is 5-8.
2. The system according to claim 1, wherein the endoscopic optical imaging system has a full field angle of 75 ° -105 °, a maximum aperture of 1.0mm, a working distance of 2mm-50mm, and a total lens length of 3.0mm or less.
3. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
ET12＞0.15mm；
ET34＞0.07mm；
0.45<R7≤0.95；
R2≥0.45；
R6>0.45；
ET2>0.37mm；
ET12 is an air gap between edges of the first lens element and the second lens element, ET34 an air gap between edges of the third lens element and the fourth lens element, R7 is a radius of curvature of an object-side surface of the fourth lens element, R2 is a radius of curvature of an image-side surface of the first lens element, R6 is a radius of curvature of an image-side surface of the third lens element, and ET2 is a thickness of a side of the second lens element.
4. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
2.5<f*TAN(HFOV)/T34<7.5；
where f is the effective focal length of the endoscopic optical imaging system, T34 is the air space between the third lens and the fourth lens on the optical axis, and HFOV is half of the maximum field angle of the endoscopic optical imaging system.
5. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
0.5mm<f*TAN(HFOV)<0.8mm；
wherein f is the effective focal length of the endoscopic optical imaging system, and the HFOV is half of the maximum field angle of the endoscopic optical imaging system.
6. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
-6.5≤f3/f<-1.5；
1.2<f4/f<1.5；
-5.0<(f3/f+f2/f)<-0.5；
wherein f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, and f is the effective focal length of the endoscopic optical imaging system.
7. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
-2.5<R4/R3<-0.5；
1.0<(R5+R6)/R7≤7.0；
-2.0<(R7-R8)/(R7+R8)<22.0；
wherein R3 is the radius of curvature of the object-side surface of the second lens element, R4 is the radius of curvature of the image-side surface of the second lens element, R5 is the radius of curvature of the object-side surface of the third lens element, R6 is the radius of curvature of the image-side surface of the third lens element, R7 is the radius of curvature of the object-side surface of the fourth lens element, and R8 is the radius of curvature of the image-side surface of the fourth lens element.
8. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
2.0<∑CT/CT2<3.5；
0.45<∑CT/TTL<0.6；
wherein Σ CT is the sum of the center thicknesses of the first lens element to the fourth lens element on the optical axis, CT2 is the center thickness of the second lens element on the optical axis, and TTL is the on-axis distance from the object-side surface of the first lens element to the image plane.
9. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
0.5<|f12/f34|<4.5；
where f12 is the combined focal length of the first lens and the second lens, and f34 is the combined focal length of the third lens and the fourth lens.
10. The system according to claim 1, wherein the endoscopic optical imaging system satisfies the following relationships:
0.3<DT41/∑AT<1.0；
where DT41 is the maximum effective radius of the object-side surface of the fourth lens, and Σ AT is the sum of the air spaces on the optical axis between any adjacent two lenses of the first lens to the fourth lens.
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